Radiation collimator for infrared heating and/or cooling of a moving glass sheet

Abstract

A glass manufacturing system and a method are described herein that use an enhanced temperature control device to help manufacture a uniformly thick glass sheet that is substantially stress free. In one example, the enhanced temperature control device includes an array of temperature controlled elements and a radiation collimator which together cool the glass sheet with a high degree of spatial resolution so as to reduce stress in the glass sheet and control the thickness of the glass sheet.

1. A method for manufacturing a glass sheet, the method comprising the steps of:
 melting batch materials to form molten glass; 
 processing the molten glass to form the glass sheet; 
 controlling heating or cooling rates across a width of the glass sheet, by adjusting temperatures of a plurality of temperature controlled elements relative to a temperature distribution across the width of the glass sheet, where the controlling step is implemented by a temperature control device which includes:
 a controller, 
 the plurality of temperature controlled elements which are connected to the controller; and 
 a radiation collimator positioned between the plurality of temperature controlled elements and the glass sheet, wherein the radiation collimator has walls which incorporate materials with a lower emissivity such that oblique rays leaving the glass sheet are reflected by the walls before reaching the plurality of temperature controlled elements, and wherein the controller individually controls the temperature of each of the temperature controlled elements such that a combination of the plurality of temperature controlled elements and the radiation collimator are able to control the temperature distribution across the width of the glass sheet with a desired spatial resolution; 
 
 drawing the glass sheet; and 
 cutting the glass sheet into individual glass sheets. 
 
     
     
       2. The method of  claim 1 , wherein the radiation collimator includes a plurality of cells where each cell has an open channel in a substantially perpendicular direction relative to the plurality of temperature controlled elements, and where each cell has walls that are in a substantially parallel direction relative to the movement of the glass sheet. 
     
     
       3. The method of  claim 2 , wherein at least one of the cells also has walls that are in a substantially perpendicular direction relative to the movement of the glass sheet. 
     
     
       4. The method of  claim 2 , wherein the controller is configured to control a temperature of each of the temperature controlled elements such that the combination of the radiation collimator and the temperature controlled elements heat or cool different portions of the glass sheet to a desired spatial resolution to reduce stress and control thickness of the glass sheet. 
     
     
       5. The method of  claim 2 , wherein each cell has the open channel with a space and the walls with a length, where the space and length have been respectively sized according to a ratio of about 10-50. 
     
     
       6. The method of  claim 2 , wherein the temperature control device further includes a frame which supports the plurality of temperature controlled elements and the radiation collimator. 
     
     
       7. The method of  claim 1 , wherein the desired spatial resolution is about 75 mm. 
     
     
       8. The method of  claim 1 , wherein the desired spatial resolution is about 50 mm. 
     
     
       9. The method of  claim 1 , wherein the desired spatial resolution is about 20 mm. 
     
     
       10. The method of  claim 1 , wherein the radiation collimator is located at least 50 mm away from the glass sheet. 
     
     
       11. The method of  claim 1 , wherein the radiation collimator is positioned away from the plurality of temperature controlled elements. 
     
     
       12. A method for manufacturing a glass sheet, the method comprising the steps of:
 melting batch materials to form molten glass; 
 processing the molten glass to form the glass sheet, wherein the glass sheet is subjected to temperature variations that occur in a direction perpendicular to a movement of the glass sheet; 
 controlling heating or cooling rates across a width of the glass sheet, by adjusting temperatures of a plurality of temperature controlled elements relative to a temperature distribution across the width of the glass sheet, where the temperature control device which includes:
 a controller, 
 the plurality of temperature controlled elements which are connected to the controller; and 
 a radiation collimator positioned between the plurality of temperature controlled elements and the glass sheet, wherein the controller individually controls a temperature of each of the temperature controlled elements such that a combination of the plurality of temperature controlled elements and the radiation collimator are able to control a temperature distribution across the width of the glass sheet with a desired spatial resolution to substantially cancel adverse affects of the temperature variations and produce the glass sheet which has little to no bands of varying retardance; 
 
 drawing the glass sheet; and 
 cutting the glass sheet into individual glass sheets. 
 
     
     
       13. The method of  claim 12 , wherein the radiation collimator is positioned away from the plurality of temperature controlled elements. 
     
     
       14. The method of  claim 12 , wherein the radiation collimator has walls which incorporate materials with a lower emissivity such that oblique rays leaving the piece of material are reflected by the walls before reaching the plurality of temperature controlled elements. 
     
     
       15. The method of  claim 12 , wherein the radiation collimator has walls which incorporate materials such that oblique rays leaving the piece of material are absorbed by the walls before reaching the plurality of temperature controlled elements. 
     
     
       16. The method of  claim 12 , wherein the desired spatial resolution is about 75 mm. 
     
     
       17. The method of  claim 12 , wherein the desired spatial resolution is about 50 mm. 
     
     
       18. The method of  claim 12 , wherein the desired spatial resolution is about 20 mm. 
     
     
       19. The method of  claim 12 , wherein the radiation collimator is located at least 50 mm away from the glass sheet.